1. Field of the Invention
The present invention relates to a system for accurately detecting the presence or absence of a misfire in an internal combustion engine. More particularly, the present invention relates to a misfire detection system for detecting a misfire repeated per 360° CA (crank angle) (i.e., an opposed cylinder misfire) with high accuracy.
2. Description of the Related Art
One known misfire detection system for a multi-cylinder internal combustion engine comprises an angular speed detecting unit for detecting an angular speed of rotation of a crankshaft during combustion of each cylinder, a first rotation change computing unit for computing a first rotation change by determining a deviation in angular speed between two cylinders in which an explosion stroke takes place successively, a second rotation change computing unit for computing a second rotation change by determining a deviation in angular speed between the two cylinders at timing before 360° CA from the timing when the angular speeds have been detected by the first rotation change computing unit to compute the first rotation change, an addition unit for adding the first rotation change computed by the first rotation change computing unit and the second rotation change computed by the second rotation change computing unit, and a misfire detecting unit for detecting a misfire generated per 360° CA by comparing the added rotation change obtained from the addition unit with a preset determination value (see Patent Document 1: Japanese Patent No. 3463476).
It has been regarded that the opposed cylinder misfire can be detected with high accuracy by using the known misfire detection system constituted as described above.